Natural History of a Highly Medically Important Snake, Russell's Viper (Daboia russelii), in a Human-Dominated Indian Rural Landscape
Venomous snakes are a public health concern in India, where they kill tens of thousands of people annually. Russell's Vipers are the major culprit, but despite their clinical significance, there is virtually no information on their ecology. I used radiotelemetry for a 9-mo period to study the spatial and behavioral ecology of a population of Russell's Vipers (Daboia russelii) in a human-dominated rural landscape in Karnataka, India. Russell's Vipers spent a substantial amount of time in plantations, which make up a significant proportion of the landscape. Snakes were the least active in March, a dry month with the hottest monthly mean maximum temperatures recorded; and spatial activity comparatively increased in late fall-early winter and May, corresponding with the timing of mating activities and the end of the dry season, respectively. Russell's Vipers basked throughout the year, but basking behavior was more frequent in January and February, when the monthly mean minimum temperatures were the lowest. The probability of observing a snake basking increased with decreasing minimum temperatures. Similarly, the snakes were found in ambush foraging postures during daytime throughout the year, and the odds of observing diurnal foraging increased with increasing minimum temperatures and was affected by an interaction between maximum temperature and sex. Overall, the data indicate that this tropical viper actively thermoregulates and is to some extent diurnal. This study provides the first quantitative field-based natural history information on Russell's Vipers, one of the most medically important snakes in the world.ABSTRACT
A satellite image of the study area in Karnataka, India. Shown on the map are the two villages Rathnapuri and Chowdikatte, the locations of the three reservoirs (R), and a transparent polygon that encompasses most of the snake locations.
Average, minimum (min), and maximum (max) temperatures (lines) and rainfall (bars, mm) by month in Rathnapuri, Karnataka, India during the study. For the temperature data, the error bars are SD.
The relationship between the number of days tracked and total distance traveled (km) of a population of Russell's Viper (Daboia russelii) in Karnataka, India. The dashed lines are the 95% prediction intervals.
Box plots of 95% minimum convex polygons (MCPs; ha) (A) and 50% MCPs (B) by sex and reproductive condition of a population of Russell's Viper (Daboia russelii) in Karnataka, India. The lines within the boxes are the medians, the boxes are the interquartile ranges, and the whiskers are the minimum and maximum values. The circle shows an extreme outlier (1.5–3 times the interquartile range). Note the different scales on the y-axes.
Monthly (untransformed) means (± SE) of distance traveled per day (A) and movement frequency (B) of a population of Russell's Viper (Daboia russelii) in Karnataka, India. For (A), the line with the circles shows the initial capture of the radio-equipped snakes, and three snakes were caught at the start of the study in late October.
Monthly (untransformed) frequency (± SE) of ambush (A) and basking (B) behaviors of a population of Russell's Viper (Daboia russelii) in Karnataka, India. The numbers above the error bars refer to the snake sample size. For (A), note that the null model was the best AICc-ranked model.
Estimates (± 95 confidence intervals) of the relationships between minimum temperature (Tmin) (A) and the sex × maximum temperature (Tmax) (B) interaction on the probability of observing a snake in ambush of a population of Russell's Viper (Daboia russelii) in Karnataka, India. On the x-axes, the vertical dashes show the distributions of the data points.
